American Pastoral was it, and he called it a life-changing experience.

Based on the Pulitzer Prize-winning Philip Roth novel, the movie is set in the 1960s Vietnam era. McGregor's character is the all-American success story - a famous high school athlete who marries a beauty queen (Jennifer Connelly) and inherits a multi-million dollar business from his father.

They live a charmed life with their daughter Merry (Dakota Fanning) until she becomes the main suspect in an act of violence and disappears from their life, shattering their American Dream.

American Pastoral opens here tomorrow.

We were at the Ritz Carlton Hotel in Toronto, where the movie premiered at this year's film festival. McGregor was sharp in a pinstriped jacket, T-shirt and jeans, with the obligatory movie star stubble, and was clearly very committed to promoting his film.

Being Scottish, he wasn't familiar with the novel that is a beloved piece of Americana. He started to read the book once he became passionate about the script.

'LIVING' IN THE STORY

"I started living in the book and I read it from cover-to-cover over and over again. There's a very fine recording on tape and whenever I was driving, I had it playing in the car. And whenever I was in a hotel room, it was playing too, and so I lived in the book for months."

He also educated himself on the Vietnam era and post-war America.

McGregor, who's best remembered for his role as Obi-Wan Kenobi in three of the Star Wars movies (Episodes I to III), did wonder if a Scotsman should have directed an American story.

"Why should this classic Pulitzer Prize-winning novel be adapted by a 45-year-old Scotsman? Maybe, why not? And it was shot by a German, and the music was composed by a Frenchman, but it was edited by an American.

"Cinema is a very international affair and I feel like the creative person isn't defined or confined by their nationality."

The father-daughter angle resonated with him as he is the father of four girls with his wife of 21 years. Though he didn't give it much thought before, he made a small comparison to the character's loss of his daughter with his own daughter leaving for college.

Actors Dakota Fanning, Ewan McGregor and Jennifer Connelly attend a special screening of American Pastoral at the Samuel Goldwyn Theater in Beverly Hills, California. PHOTO: AFP

"Not waking up at our house any more, and not being at breakfast, and not being there at night. I must have been preparing myself for that, and maybe that is why the story really hooked into my heart so much, because this is a father's story about the loss of his daughter.

"It's a very extreme and different kind of loss - he loses his daughter to radicalism and terrorism. I was preparing myself for the loss of my daughter to college, which is an easier loss, I can assure you. But maybe that is why it means so much to me and why I really understood the Swede."

McGregor has not met Roth, but knew that the author had given his blessing to the script.

"I don't know why, but I didn't ask to meet him and he didn't ask to meet me."

But the producer of the film received an e-mail from Roth that he shared with McGregor.

SEAMLESS

"It was a very, very, succinct... that he had liked our film very much and he thought the reductions that had been made from the novel to the script were good.

"The way I felt afterwards, I realised how important that it had been to me that he had liked it. If I had heard that he didn't like it, I would have thought that I had failed in some way."

Doing two jobs as actor and director wasn't difficult.

"It didn't feel like now I am the director, now I am the actor. It was all one thing. It was really quite seamless. In the three days where I didn't act, I found it a little bit boring," he said, laughing.

"There was a funeral scene and reunion scene and the Swede isn't in those scenes. They were the last three days of our shoot, and I found them to be the sort of longest three days of the shoot. I got to sit down a little bit more in those days."